1. Field of the Invention
This invention relates to a lamp receptacle with a multiple-stage power adjusting switch that is capable of disposing a screw bulb in one of an ON state, a DIM state, and an OFF state.
2. Description of the Related Art
FIGS. 1 and 2 illustrate a conventional lamp receptacle 9 for a screw bulb 90. The lamp receptacle 9 includes a dielectric seat 91 formed with first and second slots 911, 912 and a central recess 913, a multi-stage power adjusting switch 92 having a rod 921 that has one end extending into the central recess 913 and a dielectric ratchet wheel 922 connected to the end of the rod 921, a first conductive plate 93 that is mounted in the first slot 911, that is electrically connected to a power supply (not shown), and that has a first spring arm 931 extending inwardly to the ratchet wheel 922, a second conductive plate 94 mounted in the second slot 912 and having a second spring arm 941 that extends inwardly to the ratchet wheel 922, a dielectric cover 98 attached to a top end face of the seat 91 and formed with a slit 981, a conductive annular connector 95 mounted on the cover 98 and defining a bulb receiving space for receiving a conductive threaded portion 97 of the screw bulb 90, a conductive linking plate 94xe2x80x2 that is attached to the cover 98 and that has a third spring arm 942 extending inwardly to the ratchet wheel 922 and a fourth spring arm 943 extending through the slit 981 and into the bulb receiving space in the conductive annular connector 95 so as to resiliently contact the screw bulb 90, a ground terminal 96 mounted on the seat 91 and electrically connected to both the conductive annular connector 95 and the power supply, and a resistor 99 having two opposite ends that are respectively and electrically connected to the conductive linking plate 94xe2x80x2 and the second conductive plate 94.
The ratchet wheel 922 has first, second, third, fourth, fifth, and sixth ratchet teeth 9221, 9222, 9223, 9224, 9225, 9226 which are equiangularly spaced apart, and each of which has a radial side 9227 and an inclined side 9228.
The multiple-stage power adjusting switch 92 further includes a conductive bridging shroud 923 that has a central portion attached to a central portion of the ratchet wheel 922, and contact portions 9231 that are respectively attached to the inclined sides 9228 of the first, second, fourth, and fifth ratchet teeth 9221, 9222, 9224, 9225.
The rod 921 is turnable among an ON position, in which, the first spring arm 931 resiliently contacts one of the contact portions 9231 of the bridging shroud 923, and the third spring arm 942 resiliently contacts another one of the contact portions 9231 of the bridging shroud 923 so as to permit current flow through the first conductive plate 93, the first spring arm 931, the bridging shroud 923, the third spring arm 942, the fourth spring arm 943, a tungsten filament (not shown) of the screw bulb 90, the threaded portion 97 of the screw bulb 90, and the ground terminal 96, a DIM position, in which, the first and second spring arms 931, 941 resiliently and respectively contact two opposite ones of the contact portions 9231 of the bridging shroud 923, whereas the third spring arm 942 resiliently contacts one of the third and sixth ratchet teeth 9223, 9226 so as to permit current flow through the first conductive plate 93, the first spring arm 931, the bridging shroud 923, the second spring arm 941, the second conductive plate 94, the resistor 99, the fourth spring arm 943, the tungsten filament of the screw bulb 90, the threaded portion 97 of the screw bulb 90, and the ground terminal 96, and an OFF position, in which, the first spring arm 931 resiliently contacts one of the third and sixth ratchet teeth 9223, 9226 to thereby disconnect the screw bulb 90 from the power supply.
The conventional lamp receptacle 9 is disadvantageous in that the ratchet wheel 922 and the bridging shroud 923 are relative complex, and assembly thereof is laborious. Moreover, each time the rod 921 is turned from a position to another position, there are three jumps, each of which represents a respective one of the first, second, and third spring arms 931 jumping from one of the contact portions 9231 of the bridging shroud 923 and the inclined sides of the third and sixth ratchet teeth 9223, 9226 to an adjacent one of the contact portions 9231 of the bridging shroud 923 and the inclined sides of the third and sixth ratchet teeth 9223, 9226. As a consequence, the possibility of the occurrence of electric arc is increased due to the aforesaid jumps.
Therefore, it is an object of the present invention to provide a lamp receptacle that is capable of overcoming the aforesaid drawbacks.
According to the present invention, a lamp receptacle for a screw bulb comprises: a dielectric hollow seat having a peripheral wall that confines a central recess, that has a bottom end and a top end with a top face, and that is formed with opposite first and second slots extending in longitudinal directions from the top face to the bottom end and being in spatial communication with the central recess, and a channel extending in a transverse direction relative to the longitudinal directions and being in spatial communication with the central recess; a multiple-stage power adjusting switch including a rod that has a connecting end extending inwardly through the channel and into the central recess, and a dielectric ratchet wheel transverse to and secured to the connecting end of the rod, the ratchet wheel having a central portion that is connected to the connecting end of the rod, and consecutive first, second, third, and fourth ratchet teeth that are angularly disposed around the central portion, each of the first, second, third, and fourth ratchet teeth being defined by a radial side and an inclined side that is inclined relative to the central portion, the multiple-stage power adjusting switch further including a conductive bridging shroud that has a central part attached to the central portion of the ratchet wheel, and opposite first and second contact parts that are transverse to the central part and that are respectively attached to the inclined sides of the first and third ratchet teeth; a first conductive plate mounted in the first slot and having a first spring arm that extends inwardly toward the ratchet wheel so as to contact selectively and resiliently one of the first and second contact parts of the bridging shroud and the inclined sides of the second and fourth ratchet teeth of the ratchet wheel, the first conductive plate being adapted to be connected to a power supply; a second conductive plate mounted in the second slot and having a second spring arm that is opposite to the first spring arm and that extends inwardly toward the ratchet wheel so as to contact selectively and resiliently one of the first and second contact parts of the bridging shroud and the inclined sides of the second and fourth ratchet teeth of the ratchet wheel; a conductive annular connector mounted on the top face of the seat and having a threaded inner face that defines a bulb receiving space and that is adapted to engage the screw bulb threadedly; a third spring arm electrically connected to and extending upwardly and inclinedly relative to the longitudinal directions from the second conductive plate into the bulb receiving space so as to contact resiliently and electrically the screw bulb; a ground terminal mounted on the peripheral wall, electrically connected to the conductive annular connector, and adapted to be electrically connected to the power supply; and a resistor having one end electrically connected to the central part of the bridging shroud and the other end electrically connected to the second conductive plate. The rod is turnable relative to the seat among an ON position, in which, the first and second spring arms contact respectively and electrically the first and second contact parts of the bridging shroud so as to permit current flow through the first and second conductive plates, the third spring arm, the screw bulb, the conductive annular connector, and the ground terminal, a DIM position, in which, the first spring arm contacts one of the first and second contact parts of the bridging shroud electrically whereas the second spring arm contacts one of the inclined sides of the second and fourth ratchet teeth of the ratchet wheel so as to permit current flow through the first conductive plate, the resistor, the third spring arm, the screw bulb, the conductive annular connector, and the ground terminal, and an OFF position, in which, the first spring arm contacts one of the inclined sides of the second and fourth ratchet teeth of the ratchet wheel to thereby disconnect the screw bulb from the power supply.